The Art of Furniture Finishing: Part 7 – Sanding Your Piece

Welcome to Part 7 of The Art of Furniture Finishing! In this installment, we’re diving deep into one of the most critical aspects of refinishing: sanding. Whether you’re restoring an antique or transforming a thrift store find, mastering the art of sanding is essential for achieving professional results.

The Basics of Sanding

Sanding prepares your piece for its next phase, whether that’s painting, staining, or a paint wash. Choosing the right grit, understanding sanding techniques, and knowing how far to take it are all crucial to the outcome.

Scuff Sanding vs. Removing the Finish

If you’re painting your piece, a light scuff sanding is often enough to give your surface “tooth,” allowing the paint to adhere properly. A quick pass with 220 grit is typically sufficient for this. However, if you’re planning on applying a stain or paint wash, it’s best to remove the existing finish entirely. Old varnishes, lacquers, or topcoats can prevent new stains or washes from penetrating evenly, leading to blotchy results.

For a fresh, clean canvas, I recommend removing all old finishes before proceeding. This not only ensures a flawless application but also allows the natural beauty of the wood grain to shine through.

Understanding Grits and Graduating Grits

When sanding, grit progression is key. Sanding begins with coarse grits to remove finishes or imperfections and moves to finer grits to smooth the surface. Each grit serves a unique purpose:

   •   Coarse Grits (40-80): These are your heavy lifters, perfect for stripping finishes or leveling rough surfaces.

   •   Medium Grits (120-180): Ideal for preparing the wood for stains or paints. My personal go-to is 150-180 grit, especially when I’m planning to stain or apply a paint wash.

   •   Fine Grits (220-320): Best for achieving a smooth surface, but if you’re staining, avoid going beyond 220 grit as it can over-soften the wood, preventing proper stain absorption.

Tip: Always follow the manufacturer’s recommendations for grit levels on the products you’re using. They’ve been tested to perform best under specific conditions.

Tools of the Trade: Sanders

Not all sanders are created equal, and understanding their uses can save you time and effort:

   •   Orbital Sanders: Great for general sanding and smoothing flat surfaces. My favorite is the Festool ETS 125, which delivers precision and lasts a lifetime (as long as you register it for the warranty!).

   •   Detail Sanders: Perfect for getting into tight corners or intricate carvings. The Festool RTS 400 is my go-to for detailed work.

   •   Belt Sanders: These are heavy-duty tools for removing thick finishes or material quickly, though they require a skilled hand to avoid gouging the wood.

If Festool isn’t in your budget, the Dewalt orbital sander is a reliable alternative. However, from personal experience, I’ve burned through several motors on the Dewalt sanders early in my refinishing days. Investing in quality tools like Festool not only saves you money in the long run but also ensures consistent results.

Dust Control: The Unsung Hero

Sanding can create a dusty mess, but a dust extractor can make a world of difference. My dust extractor has been one of the best investments in my refinishing journey. Not only does it keep my workspace clean, but it also improves air quality and minimizes cleanup time.

Key Takeaways for Sanding Success

   •   Always graduate through grits to ensure a smooth, even surface.

   •   Stop at 150-180 grit if staining or doing a paint wash to maintain the wood’s ability to absorb.

   •   Invest in high-quality sanders and tools to achieve professional results.

   •   Don’t forget to check the manufacturer’s grit recommendations for the products you’re using.

For those looking to upgrade their sanding setup, here’s a link to my favorite sanders and detail sanding products.

Swirl Marks: What Causes Them and How to Prevent Them

Swirl marks are a common frustration when sanding, especially for beginners or when using improper techniques. These unsightly circular scratches can show through your finish, ruining an otherwise smooth surface. Understanding what causes swirl marks and how to avoid them will save you time and ensure a flawless end result.

What Causes Swirl Marks?

Swirl marks are typically caused by:

   •   Using the Wrong Sandpaper: Low-quality sandpaper or sandpaper that’s worn out can leave uneven scratches.

   •   Skipping Grits: Jumping from a coarse grit to a fine grit without proper grit progression leaves deeper scratches that finer grits can’t fully remove.

   •   Improper Technique: Pressing too hard on the sander or not moving it evenly across the surface can cause uneven sanding.

   •   Dirty Sandpaper: Sandpaper clogged with debris or dust can drag particles across the surface, creating scratches.

   •   Poor Dust Extraction: Dust and debris left on the surface can get caught under the sandpaper and create swirl marks.

How to Prevent Swirl Marks

1. Use High-Quality Sandpaper: Invest in premium sandpaper designed for your sander. Cheap sandpaper may break down quickly or leave uneven scratches.

2. Follow a Proper Grit Progression: Always move systematically through grit levels (e.g., 80 → 120 → 150 → 180). This smooths out scratches from the previous grit before moving to finer ones.

3. Let the Sander Do the Work: Avoid pressing too hard. A quality sander like the Festool ETS 125 or RTS 400 is designed to do the work with minimal pressure. Let it glide across the surface.

4. Keep Sandpaper Clean: Check your sandpaper frequently. If it’s clogged, replace it or clean it with a sandpaper cleaning block to prevent dragging particles across the surface.

5. Use a Dust Extractor: A good dust extractor minimizes debris on the surface and in the air. This prevents dust from getting caught between the sandpaper and wood, reducing the risk of swirl marks.

6. Check Your Technique: Keep your sander moving in slow, even passes. Never stay in one spot too long, as this can create uneven sanding patterns.

Fixing Swirl Marks

If you notice swirl marks after sanding, don’t panic! Most can be corrected with a finer grit. Start by sanding lightly with a grit just above your last one (e.g., if you stopped at 150, go to 180) and ensure your surface is completely clean and dust-free before continuing.

By taking these precautions and focusing on technique, you can prevent swirl marks and achieve a beautifully smooth surface every time. This extra attention to detail will make a noticeable difference in the quality of your finished piece.

With the right tools, techniques, and patience, sanding can transform a rough piece into a stunning masterpiece. Happy refinishing, and stay tuned for the next chapter in The Art of Furniture Finishing!